LETTERS TO BROTHER JOHN. 141 



ducts of the salivary glands ; that is to say, it sti- 

 mulates the mouths of these excretory ducts : and 

 this stimulation is propagated along the ducts to 

 the glands themselves the liver and pancreas. 

 These glands, so stimulated, pour out an increased 

 quantity of their individual secretions; viz. bile, and 

 pancreatic juice. The surface of the bowel itself, 

 too (the duodenum), pours out an increased quantity 

 of fluid, called " the intestinal juice." The chyme 

 mingling with these juices, another remarkable 

 change is effected : the chyme is no longer chyme ; 

 it has lost its identity ; and the result is, a milky 

 fluid, called " chyle," destined to become blood ; and 

 an excrementitious matter the dross, if I may so 

 speak destined to be expelled from the body by 

 the bowels. 



This conversion of the chyme into chyle forms 

 the second great change ; by which that which was 

 once food bread and me&t has been advanced 

 two degrees more nearly to the nature of blood. 



I hope you have not yet forgotten that the chy- 

 lous absorbents arise, by open mouths, from the 

 internal surface of the bowels. As the chyle, 

 therefore, flows along the duodenum, it comes into 

 contact with the same open mouths of the chylous 

 absorbents. These, by virtue of their sensibility, 



